I couldn’t find an exact model number or name for this tram, but it’s one of the first electric trams manufactured by Siemens and introduced in Frankfurt (Germany) in 1884 (PDF file hosted on the Internet Archive). It was a commuter tram connecting Frankfurt and Offenbach (that’s why it says “Frankfurt-Offenbach-Trambahn” on the side), and apparently, it was the world’s fourth electric tram line (This Wikipedia article is only available in German, unfortunately, but you can use a website translation tool or dump chunks of text into DeepL). Most of these trams no longer exist, as only a couple of them made it into a museum.

The exact number of passengers they could carry varies from source to source, but it’s usually twenty-some passengers. According to the Siemens PDF linked above, their first electric tram from 1881 was five metres long and two metres wide, carrying up to 20 passengers at a time. The 1884 model in this post looks similar, maybe a bit longer than the 1881 model, so I’d say that 25-ish passengers sounds accurate enough. This includes both seated and standing passengers.

Fun fact: The smaller 1881 model is only slightly larger than many modern cars but can transport more than three times the amount of people.